Wireless duplex signaling system



EALQQSQQB M. M. DOLMAGE. WIRELESS DUPLEX SIGNALING SYSTEM. APPLICATION FILED :uwu. 19m.

Patented May 2, 1922..

1i rreo STATES PATENT orrice.

WIRELESS DUPLEX SIGNALING SYSTEM.

Specification of Letters Patent.

Application filed July 15, 1918. Serial No. 245,101.

To all who-m. it may concern:

lie it known that I, MIHRAN M. DOLMAGE, a citizen of the United States, residing at 825 Vermont Avenue NW., Washington, in the District of Columbia, have invented certain new and useful Improvements in Wireless Duplex Signaling Systems, of which the follm ving is a specification.

This invention relates to a wireless duplex signaling system. Its object is to pro-- vide a system for the simultaneous transmission and reception of signals and in particular to provide means for two way wireless telephone communications.

To secure successful wireless duplex operation, it is necessary to render the receiving equipment free from the interference by the transmitting equipment at the same station. 'lhe-re are a number of systems available to the art at the present time for accomplishing this purpose, some depending upon lay whlch controls the direction of transmisthe use of two different freqpenc-ies for transmission and rece1v1ng, ot er systems dependent upon the use of a compensating In all such cases, some approach is made to true duplex operation, but never accomplished absolutely. Where long range wireless operation is concerned, the magnitude of the transmission currentv is so enormously greater than that excited in the antenna by the received waves of low amplitude, that no real hope can be entertained to secure duplex operation by local compensating circuits of differential character, so far as the reception of signals is concerned, even when a different frequency is used for receiving and for transmitting, and the receiving circuit is sharply tuned for this purpose.

This invention utilizes voice operated circuit changing means which control the circuits of the duplex wireless system in such a way as to completely eliminate the reaction of the transmitted energy upon the receiving apparatus at the transmitting station. (-ircuit changing means, voice controlled in their operation, have heretofore been disclosed. This invention differs, however, from most previous inventions inthat it does not require the operation of a switch for putting the transmitting apparatus into electrical connection with the antenna. In the system described herein, the transmitting antenna. etc.

certain and positive character.

apparatus as well as the receiving apparatus at the wireless station are normally connected to the antenna. No part of a sentence spoken into the transmitter at the wireless station is distorted or lost during the time interval required for establishing a condition for proper transmission, as in the sysbe completely shielded from the effect of signals radiated by other wireless stations, also from static impulses or grinders which. may reach the circuit changing means via the antenna. If such shielding is not provided for, false operations would result. In the invention herein disclosed, the voice operated resion is connected to points of the same potential, under all conditions, for all waves received by the antenna Whether useful or lnterfering in character. In this respect the system herein disclosed is therefore completely free from all false operations of the control relay.

A further important advantage of the system described herein consists in the utilization of devices for amplifying the controlling voice currents so that the operation of the circuit changing means may be made of The use of such amplifying devices has been indicated in conjunction with the particular duplex wireless circuit shownin attached drawings, but it is clear that such devices may be used Patented May 2, 1922..

with any other wireless duplex signaling circuits, depending for their operation upon the utilization of voice operated circuit changing means. A practical solution is shown in the utilization of a device of the type known as an audion, which can be made to amplify alternating currents of both audio and radio frequencies into direct current. It then becomes possible to use direct current electromagnetic relays, which usually can be made more sensitivefthan al ternating current relays'for the purpose of securing the proper transmitting and receiving relations in the duplex wireless system. In place of an audion any other device having similar characteristics, such as a kenotron (General Electric Review vol. XVIII, page 1561) or a pliotron (General Electric Review, vol. XVIII, page 327) may be used.

This invention is illustrated in its fundamental features in Fig. 1 and Fig. 2. A modification of the arrangement shown on Fig. 1 is indicated on Fig. 2. Referring first to Fig. 1, 1 is an antenna for the simultaneous transmission and reception of signals. Antenna 1 includes two parallel branches which are also in series with the primary of receiving transformer 18. One branch includes primary winding of coil 2 of automatic con- "trolling circuit A and secondary winding of transformer 6. The other branch includes primary winding of coil 3 of automatic controlling circuit A, and an artificial line comprising inductive resistance 4: and condenser 5. It is contemplated to. have the artificial line balance very accurately the transmitting circuit of the duplex system. This arrangement neutralizes completely the electromotive forces generated in the secondary Windings of coils 2 and 3, on all received signals. Transformer 6 is connected to the plate circuit of a vacuum tube modulator 7 (such as an audion or pliotron). The grid circuit of this same tube 7 is connected to condenser 8-which in turn is bridged by modulatin transformer!) and transformer 11. The pr1- mary winding of transformer 11 is connected to a suitable source 12 of high frequency currents. The secondary windings of coils 2 and 3 are closed through condenser 13 which, is bridged by the grid circuit of a vacuum tube amplifier 14. The plate circuit of this same tube 14 is bridged by resistance 15, which in turn is bridged by relay 17 and condenser 16. The receiving of signals is obtained through transformer 18, its secondary winding bridged by tuning condenser 19. Bridged around the tuning condenser is the Vacuum tube amplifier 20 with its component grid, filament and plate circuits. The plate circuit of tube 20 is connected through transformer 21 and tuning condenser 22 to a second vacuum tube detector 23 with its corresponding filament, grid and plate circuits. The plate circuit is closed through by resistance 24 and the usual receiving telephone 26 and condenser 25. Fig. 2 is an alternative arrangement for that shown in elements 15, 16 and 17 of Fig. 1. In place of the alternating current relay 17 a direct current relay 27 is substituted. Element 14, when used in conjunction with the arrangement of Figure 2, is a device for rectifying and amplifying alternating currents, instead of being merely an amplifier which is the sole function it performs when used in conjunction with the arrangement shown on Figure 1. When radio frequency currents are being emitted, there will be, on account of the rectif ing qualities of bulb 14, unidirectional. impu ses through relay 27, which would operate. To prevent the operation of this relay when the transmitter is not being spoken into, a direct current electromotive force is applied through an adjustable resistance, balancing to an degree that may be found desirable the unidirectional impulses through relay 27. When,however, voice impulses are impressed upon the transmitter, the electrical balance above described will be destroyed, resulting in the o eration of relay 27, which is the end desired In a circuit of the character outlined above, the following operation will obtain. High frequency currents generated by source 12, are amplified by tube 7 andthen transmitted through transformer 6. These high frequency currents reach the antenna through coil 2 and are radiated by. the antenna into space. These radio fr uency currents also penetrate into coil 3 arid balancing artificial circuit comprising the elements 4' and 5. The electromotive forces generated in the secondary windings of coils 2 and 3 are cumulative in their effect and act upon the grid circuit of tube 14:. Radio frequency currents, therefore, flow through condenser 16 and relay 17. They'have no effect, however, upon relay 17, no more than sustained or non-modulated radio frequency currents received from distant oints have any effect upon receiver 26. owever, when transmitter 10 is spoken into, and a modulation secured in the amplitude of the high frequency currents generated by source 12, then the audio frequency variations of these high frequency currents will operate alternating current relay 17. This relay operates during the time the transmitter is spoken into and short circuits tuning condenser 22, thereby preventing any of the transmitted audio frequency impulses fromreaching receiver 26. This receiver therefore remains absolutely silent. On signals received by the antenna, on account of the electrical association of coils 2 and 3, in the manner shown, and as previously described,'the two terminals of condenser 13 will be at the same potential. This result follows, since, by construction, on received signals the electrical impedance of artificial balancing circuit comprising elements 3, 4, and 5 is equal to the impedance of the transmitting circuit comprising elements 2 and 6. The electromotive forces generated in the secondaries of coils 2 and.3 will consequently be equal and opposite in phase. Hence no high fre-' quency current circulates, on received signals, in the circuit of the secondaries of coils 2 and 3. No high frequency currents nor scream i audio frequency mOdUIlLtIOIISOf-SUClIC111- rents penetrate, therefore, intothe grid circuit of vacuum "tube amplifier 14-. Therefore, the two terminals of relay 1 7, during receiving, are at the same potential. 'ilhis relay, therefore, cannot operate on received signals. Relay 17 is not actuated, therefpre,

on receiving. Radio frequency currents reaching transformer 18 will therefore reach their destination unhampered and the receiving will be obtained in full amplitude at receiver 26.

" It is clear from the above description that this invention is not inan way limited to any one particular type. 0 wireless signaling system. What is characteristic of th1s system is the use of an auxiliary circuit, of a control rela' in this auxiliary circuit ac-. tuated by au io requency modulations of the transmitted radio frequency currents, with balancing artificial circuit, substan-' tially as described. Instead of using a control rela of alternatingcurrent type, I find it desira 1c in some cases to use a very sensitive direct-current relay in association with a counterbalancing electromotive forcef,

the above combination taking the place 0 the alternating current relay 17 and condenser lfi.

What I claim is:

1. In a system for the transmission and the reception of wireless signals, an antenna, transmitting apparatus normally connected to said antenna, an auxiliar circuit, a device for rectifying and ampllfying alternating currents in said auxiliary circuit, a

control relay associated with the aforesaid device responsive to the currents rectified and amplified by the aforesaid device, re-

ceiving apparatus normally connected to the antenna, and means under the control of the aforesaid relay rendering inoperative the receiving apparatus when said system is used for transmission.

2. In a system efqr. the transmission and reception of wir'elsssignals, an antenna, transmitting apparatus normally connected to said antenna, an auxiliary circuit, a second circuit balancing the transmitting circult on receiving signals, a control relay in said auxlllary circuit, receiving apparatus normally connected to the antenna, and

means under the control of the aforesaid relay rendering inoperative the receiving apparatus when said system is used for transmission.

3. In a system for the transmission and reception of wireless signals, an antenna, transmitting apparatus normally connected to said antenna, an auxiliary circuit, a second circuit balancing the transmitting circuit on received signals,ca device for rectifying and amplifying alternating currents in said auxiliary circuit, a control relay re-' sponsive to the currents amplified and rectified by aforesaid device, receiving apparatus normally connected -to the antenna, and means under the'control of aforesaid relay rendering inoperative the receiving apparatus when said system is used for transmission. 7

4. In a system for the transmission and reception of wireless signals, an antenna, transmitting apparatus normally, connected to said antenna, an auxiliary circuit, a second circuit balancing the transmitting circuit on received signals, means for connecting said auxiliary circuit with said transmitting circuitand said balancing circuit, a control relay connected to points of equal potential for received energy in aforesaid auxiliary circuit, receiving apparatus normally connected to the antenna and means under the-control of aforesaid relay rendering inoperative the receiving apparatus when said system is used for transmission.

5. In a system for the transmission and reception of wireless signals, an antenna, transmitting apparatus normally connected to said antenna, an auxiliary circuit, a second circuit balancing the transmitting circuit, means for connecting said auxiliary circuit with said transmitting circuit and said balancing circuit, a device for rectifying and amplifying alternating currents connected 'to points of equal potential on received signals in the aforesaid auxiliary circuit, a control relayassociated with the aforesaid device responsive to the currents rectified and amplified by the aforesaid device, receivmg apparatus normally connected to the. antenna, and means under the control of the aforesaid relay rendering inoperative the receiving apparatus when said system is used for transmission.

6. In a system for the transmission and reception of wireless signals, the combination of an antenna, transmitting apparatus normally connected to the antenna, receiving apparatus normally connected to the antenn'a, connections to a wire telephone system, with circuit changing means controlled directly by electric currents predominatingly of audio frequency character and arranged to render ino erative the receiving apparatus when sai system is used for transmission.

7. In a system for the transmission and receptioh of wireless signals, the combination of an antenna, receiving apparatus, a

source of radio frequency currents, connec- I tions to a wire telephone system, a modulator, a demodulating tube, circuit changing means controlled by the resulting demodulated currents and arranged to render inop-- for the transmission andv reception of wireless signals, the combinathe receiving apparatus when said system is I tion 0 an antenna, transmitting, apparatus used for transmission. 10, normally connected to the antenna, receiv- In testimony whereof I afiix my signature ing 7 apparatus normally connected to the in presence of two witnesses.

antenna, with voice controlled circuit chang MIHRAN M. DOLMAGE. ing means completely shielded from all for- Witnesses:

eign interfering waves received through the E. F. BUDD,

antenna and arranged to render inoperative O. D. RATOLIFFE. 

